全新java初学者实践教程6(Java SE5.0版)
=lB+GS% 基本语法3
7Gwn ,&) 7+_TdDBYs - BQoNEh 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
&8p]yo2zO -|K^!G [font="Times] 1.循环语句[font="Times]:while,do-while,for
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X:N`x [font="Times]2.分支语句[font="Times]:if-else,switch,
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tuT>,BbR 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
>A5*=@7bY? [font="Times]
x*H,eY3 4.异常处理语句[font="Times]:try-catch-finally,throw
5;WESk p.wed%O. 实践:
bsuGZ [font="Times] 1.循环语句
N>pTl$\4 [font="Times] while 语句
s2Z'_rT [font="Times]class While {
^/6LVB * [font="Times]public static void main(String args[]) {
n["G
ry [font="Times]int n = 10;
[3K& cX}B [font="Times]while(n > 0) {
.rPg [font="Times]System.out.println("tick " + n);
0tz7^:|D [font="Times]n--;
RSfB9)3D [font="Times]}
Nm{+!}cC [font="Times]}
k|hy_? * [font="Times]}
'6g;UOx^= [font="Times] do…while 语句
53X i) [font="Times] class DoWhile {
Lm-f0\( [font="Times]public static void main(String args[]) {
Y0z)5),[U: [font="Times]int n = 10;
u0Q6+U [font="Times]do {
:9H`O!VF [font="Times]System.out.println("tick " + n);
*x!j:/S`n [font="Times]n--;
,=a+;D]' [font="Times]} while(n > 0);
rF^H\U:w [font="Times]}
=I.uf [font="Times]}
,+P2B%2c 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
V7 OhOLK8 [font="Times] for语句
p=XEMVqm [font="Times] class ForTick {
~|Nj+A [font="Times]public static void main(String args[]) {
5)c B\N1u [font="Times]int n;
/KTWBcs 7 [font="Times]for(n=10; n>0; n--)
WJlJD*3 [font="Times]System.out.println("tick " + n);
9^?2{aP% [font="Times]}
W-RqooEv [font="Times]}
o[aP+O Md 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
sC'PtFK8z 还有啊,[font="Times]for循环的部分可以为空的
Hg~8Td** [font="Times]class ForVar {
u?4d<%5R! [font="Times]public static void main(String args[]) {
]."t [font="Times]int i;
og?L 9 [font="Times]boolean done = false;
<YM!K8hu$ [font="Times]i = 0;
,. HS )<B [font="Times]for( ; !done; ) {
GU0[K#% [font="Times]System.out.println("i is " + i);
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u [font="Times]if(i == 10) done = true;
yHo#v:>?p [font="Times]i++;
5oe{i/#di [font="Times]}
XI'.L ~ [font="Times]}
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循环语句的例子下载 3dx.%~c [font="Times] 2.分支语句[font="Times]
2Rqpok4 [font="Times] if/else语句
);/p[Fd2] [font="Times]class IfElse {
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[font="Times]public static void main(String args[]) {
!GJT-[ [font="Times]int month = 4; // April
jA? 7>"| [font="Times]String season;
sis1Dh9: [font="Times]if(month == 12 || month == 1 || month == 2)
Ou_2UT [font="Times]season = "Winter";
lMmP]{.>$ [font="Times]else if(month == 3 || month == 4 || month == 5)
Doe:m#aNj [font="Times]season = "Spring";
58t_j54 [font="Times]else if(month == 6 || month == 7 || month == 8)
Hf+oG [font="Times]season = "Summer";
)+Yu7=S [font="Times]else if(month == 9 || month == 10 || month == 11)
sk5B} - [font="Times]season = "Autumn";
pwvmb\ [font="Times]else
V$_.&S?(Y [font="Times]season = "Bogus Month";
~J0r%P [font="Times]System.out.println("April is in the " + season + ".");
v"*c\, [font="Times]}
Elt"tJ [font="Times]}
,*sKr)9) [font="Times]//这段程序输出[font="Times]:
e**5_L [font="Times]//April is in the Spring.
(~NR."s; [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
NE><(02qW [font="Times] switch语句
ck$> [font="Times] class Switch {
ub2B!6f a [font="Times]public static void main(String args[]) {
t:P]G>)x| [font="Times]int month = 4;
<OrQbrWQa [font="Times]String season;
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q [font="Times]switch (month) {
yJ>Bc [font="Times]case 12:
d/b\:[B@ [font="Times]case 1:
Z6nQW53- [font="Times]case 2:
O[$XgPM [font="Times]season = "Winter";
[M#(su0fv [font="Times]break;
^SbxClUfw! [font="Times]case 3:
P\h1%a/D [font="Times]case 4:
tlYB'8bJY [font="Times]case 5:
I0N~>SpZ5 [font="Times]season = "Spring";
hb(H-`16 [font="Times]break;
[sK'jQo-[1 [font="Times]case 6:
S
rhBU6K [font="Times]case 7:
Of-8n- [font="Times]case 8:
:|-^et]a8 [font="Times]season = "Summer";
i&-g [font="Times]break;
9fYof [font="Times]case 9:
+.v+Opp, [font="Times]case 10:
59(kk; [font="Times]case 11:
YXg^t$ [font="Times]season = "Autumn";
Xif>ZL?aXb [font="Times]break;
Z ?ATWCa [font="Times]default:
@vO~'Xxq! [font="Times]season = "Bogus Month";
!>WW(n07Ma [font="Times]}
;,Os3 [font="Times]System.out.println("April is in the " + season + ".");
P!!:p2fo [font="Times]}
k;<F33v;Mh [font="Times]}
分支语句代码下载 Gb.}af#v L>rW S-
[font="Times]switch语句适合于条件非常多的逻辑
WV;[v g] 请看上述语句可以混合使用,请看
下载例子